JP2000091708A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element which can keep barrier effect for overflow of electron from an active layer and reduce barrier working on flow-in of hole to the active layer. SOLUTION: An overflow prevention layer 12 is provided as to work as a barrier to suppress the overflow of electrons injected to an active layer 106 and its barrier working on a hole before injecting electrons to the active layer 106 is released. Specifically, by forming a superlattice where the layer thickness or composition gradually changes or a structure where the composition changes continuously or stepwise, the flow-in of the hole is promoted and the loss of carrier is eliminated so that a semiconductor light emitting element superior in light emitting efficiency can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor light emitting device. More specifically, the present invention relates to a semiconductor light emitting device that can reduce a barrier against inflow of holes into an active layer while maintaining a barrier effect against overflow of electrons from the active layer.

[0002]

2. Description of the Related Art In a semiconductor light emitting device, in particular, a semiconductor laser device or a high-brightness light emitting diode (LED), it is necessary to confine carriers at a high density in an active layer which emits light. In order to more completely confine carriers, a structure having a so-called cap layer has been proposed. This cap layer has a role to prevent overflow, that is, outflow of carriers from the active layer.

In the following description, a semiconductor laser using a nitride semiconductor will be described as an example of a semiconductor light emitting device. Note that the "nitrogen-based semiconductor" in the present _{application, B x In y Al z Ga} (1-xyz) N (O ≦ x,
y, z ≦ 1), and a group V element includes a mixed crystal containing phosphorus (P), arsenic (As), etc. in addition to N. Further, a group II such as BeCN ₂
It shall also include compounds of Group IV -N ₂ type.

[0004] The nitride semiconductor is magnesium (Mg).
Attention has been paid to the success of p-type doping using GaN, and various semiconductor laser structures in a blue visible light wavelength band and an ultraviolet wavelength band have been proposed. However,
Stable laser oscillation has not been realized yet, and many problems to be solved remain. One of the big problems is
The operating voltage and the threshold current are extremely high. The cause is that multiple quantum wells (MQW: mult
The barrier of the iple quantum well is not high enough for the well. This is because, in the case of a gallium nitride based semiconductor, the lower the indium composition of the well layer, the higher the luminous efficiency. That is, in order to improve the luminous efficiency of the well layer, it is necessary to lower the indium composition. However, the band gap of the well layer becomes large, and a sufficient energy difference from the barrier layer is required. Can not.

As a result, a large number of carriers, especially electrons, overflow into the guide layer and the cladding layer, causing loss. Aluminum (Al) for cladding layer
The overflow can be reduced by increasing the composition of On the other hand, in order to achieve sufficient light confinement, the cladding layer needs to be formed thick. However, when the cladding layer is grown thicker by increasing the aluminum composition, cracks occur, and while suppressing the occurrence of cracks,
It has been difficult to grow thick AlGaN cladding layers.

On the other hand, there has been proposed a structure in which a cap layer having a high aluminum composition is provided between an active layer and a guide layer.

FIG. 10 is a schematic sectional view showing a semiconductor laser provided with such a cap layer.

Documents disclosing this structure include, for example, Japanese Patent Application Laid-Open No. 9-219556 and Proc. 2nd Int. Conf. Nitr
ideSem. S1 (1997) p. 444. The semiconductor light emitting device shown in FIG. 10 has an n-type contact layer 102, n on a sapphire substrate 101.
Type cladding layer 104, n-type light guide layer 105, active layer 1
06, the p-type cap layer 112, the p-type light guide layer 107,
It has a structure in which a p-type cladding layer 108 and a p-type contact layer 109 are stacked in this order.

The cladding layers 104 and 108 need to have a larger band gap than the active layer in order to confine carriers in the active layer 106 and obtain a high optical output from the active layer.

[0010] Each of the p-type layers is processed into a mesa shape as shown in the figure to narrow the injection current. The side surface of the device is covered with a protective film 110 made of SiO2 or the like, an n-side electrode 103 is formed on the p-type contact layer 102, and an n-side electrode 1 is formed on the p-type contact layer 109.
11 are formed. The material of each layer is, for example, GaN as the n-type contact layer 102 and the n-type cladding layer 104.
AlGaN, and Ga as the n-type light guide layer 105
N, a multiple quantum well (MQW) made of InGaN as the active layer 106, and AlGa as the p-type cap layer 112.
GaN can be used as the N and p-type light guide layers 107, AlGaN can be used as the p-type cladding layer 108, and GaN can be used as the p-type contact layer 109.

The n-side electrode 103 is formed by stacking, for example, aluminum (Al), platinum (Pt), and gold (Au) in this order, and the p-side electrode 111 is formed of, for example, platinum (Pt) and gold (Au). Au) can be used in this order.

In the semiconductor laser shown in FIG.
By providing the cap layer 112, the overflow of electrons to the p-type guide layer and the p-type clad layer can be suppressed to some extent.

[0013]

Conventionally, an AlGaN cap layer 112 having a high aluminum composition has been used to prevent the overflow of electrons, and the AlGaN cap layer 112 is formed by making the layer thinner and highly doped. ,
It was believed that the holes could easily flow into the active layer.

However, as a result of the study by the present inventor, it has been found that this recognition is erroneous, that it is difficult for holes to flow into the active layer, and that a large loss occurs in the laser element. Hereinafter, the reason will be described in detail.

FIG. 11 is a conceptual diagram showing the band structure of the device of FIG. 10 and illustrating the flow of carriers under the condition of a low injection current. As shown in the figure, the cap layer 112 made of AlGaN has a Schottky barrier of about 150 meV between the valence band and the p-type guide layer. Since the holes have a large mass and a low mobility in the gallium nitride based semiconductor, they exceed the energy barrier of the p-type AlGaN
Is difficult to reach. Holes are in the cap layer 112
A very high electric field is required to be injected into the active layer beyond the barriers, and this is limited to high applied voltages to the laser and high injection levels. That is, under the low injection condition, the inflow of holes into the active layer is restricted by the cap layer 112 as shown in FIG.

On the other hand, electrons flowing into the active layer 106 have a much higher mobility, and have a long lifetime because no holes to be recombined exist in the active layer. Have. As a result, the electrons in the active layer overflow the cap layer 112 to the p-type guide layer 107, and recombine with holes in the guide layer to emit light.

This process causes a large loss of carriers. Further, in order to improve the performance of such a semiconductor laser, a structure using a clad layer made of a superlattice is disclosed in Japanese Patent Application Laid-Open No. 10-84134 (inventor: Nakamura et al.).
However, the above-mentioned problem has not been solved.

On the other hand, as a method for solving this problem, p
It is also conceivable to dope the type AlGaN cap layer 112 with magnesium (Mg) at a high concentration. However, this has two problems as described below.

That is, the first problem is that p-type AlGaN
The upper limit of the hole carrier concentration is limited to about 10 ¹⁷ cm ⁻³ , which makes it difficult to dope at a high concentration.

The second problem is that the doping efficiency of p-type AlGaN is extremely low, and excessive magnesium is generated at the uppermost doping level. This excess magnesium diffuses very easily into the active layer even during the operation of the light emitting element, causing a significant decrease in the luminous efficiency of the active layer.

Because of these problems, the cap layer 1
It is difficult to dope 12 to a high concentration.

On the other hand, a problem peculiar to a light emitting device using a nitride-based semiconductor is that a cap layer 11 made of AlGaN is used.
It was also found that the provision of No. 2 causes deterioration with time of the emission intensity. This is presumably because trap levels for holes are generated in the guide layer due to the difference in lattice constant between the cap layer and the guide layer.

As described in detail above, it has been found that in the conventional semiconductor laser using the AlGaN cap layer, the inflow of holes into the active layer is hindered, which causes a large loss in the laser element. Further, if an attempt is made to dope the cap layer with a high concentration in order to prevent this, another problem arises. It was also found that there was a problem that a hole trap level was generated.

The present invention has been made based on the recognition of such a problem. That is, an object of the present invention is to provide a semiconductor light emitting device that can reduce a barrier against inflow of holes into an active layer while maintaining a barrier effect against overflow of electrons from the active layer.

[0025]

According to the present invention, an overflow prevention layer having a unique structure is introduced.

That is, the semiconductor light emitting device of the present invention comprises an active layer, and emits light by injecting electrons and holes into the active layer. The semiconductor device further includes an overflow prevention layer acting as a barrier for suppressing overflow of one of the electron and the hole, and the overflow prevention layer further includes any one of the electron and the hole before being injected into the active layer. Or the barrier effect on the other is reduced.

Alternatively, the semiconductor light emitting device of the present invention comprises an active layer and an overflow prevention layer, and emits light by injecting electrons and holes into the active layer. The overflow prevention layer has a first band gap that is larger than the active layer and changes steeply on the end face on the active layer side, and has an end face in the layer thickness direction on the opposite side when viewed from the active layer. An effective band gap is configured to be smaller than the first band gap as approaching.

Here, as a preferred embodiment of the present invention, the overflow prevention layer has a superlattice including a plurality of barrier layers and a plurality of well layers, and the plurality of barrier layers and the plurality of well layers are provided. Is characterized in that the layer thickness or the composition is not constant.

Alternatively, the overflow prevention layer has a portion in which the composition changes continuously along the thickness direction of the layer.

Alternatively, the overflow prevention layer has a portion where the composition changes stepwise along the layer thickness direction.

The present invention is particularly suitable for use in a semiconductor light emitting device using a nitride-based semiconductor. Specifically, the active layer is made of a nitride-based semiconductor, and the overflow prevention layer is made of aluminum. It is suitable for use in a semiconductor light emitting device made of a nitride semiconductor containing.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, by introducing an overflow prevention layer having a unique structure, carrier loss can be effectively suppressed, the luminous efficiency is higher and the life is longer than before. A semiconductor light emitting device having a low threshold current density and a low operating voltage can be realized.

Hereinafter, embodiments of the present invention will be described with reference to a semiconductor laser using a nitride-based semiconductor as an example.

FIG. 1 is a schematic sectional view showing a semiconductor light emitting device of the present invention. That is, the semiconductor light emitting device illustrated in FIG. 1 is a semiconductor laser using a nitride semiconductor.
In this semiconductor laser, an n-type contact layer 102 and an n-type clad layer 10 are formed on a sapphire substrate 101.
4, an n-type light guide layer 105, an active layer 106, an overflow prevention layer 12, a p-type light guide layer 107, a p-type cladding layer 108, and a p-type contact layer 109 are laminated in this order.

The role, composition, and layer thickness of each layer can be the same as those described above with reference to FIG. 10, so the same portions are denoted by the same reference numerals and detailed description thereof will be omitted. Each of the p-type layers is processed into a mesa shape as shown in the figure to narrow the injection current.
In order to confine current and confine light, for example, in addition to the illustration, for example, a selective buried ridge type (Selectivel ridge type) may be used.
Various structures such as a y-buried ridge (SBR) laser and an isolated stripe laser may be employed.

The feature of the semiconductor light emitting device of the present invention resides in the overflow prevention layer 12 provided between the active layer 106 and the guide layer 107.

FIG. 2 is a conceptual diagram of a valence band structure showing a specific example of the overflow prevention layer of the semiconductor light emitting device of the present invention. That is, FIG. 3 shows the energy level of the valence band of the overflow prevention layer 12. In the example shown in the figure, the overflow prevention layer 12 is made of AlGaN
Layer 12B made of GaN and well layer 12 made of GaN
It has a superlattice structure in which W is alternately stacked. The superlattice is designed to gradually change the effective energy level from the low energy guide layer toward the active layer. The specific structure can be appropriately designed according to the well and barrier materials. By optimizing the material and layer thickness of the superlattice, the characteristics of the light emitting element can be controlled, and desired characteristics can be realized. That is, it is possible to provide a light-emitting element having higher efficiency and longer life than before.

In the specific example shown in FIG. 2, as the distance from the guide layer 107 to the active layer 106 increases, the barrier layer 1
The layer thickness of 2B is gradually increased, and the layer thickness of well layer 12W is formed to be thinner on the contrary. Further, in the example of the figure, the Al composition of each barrier layer is the same.

As described above, when the thickness of each layer constituting the superlattice is gradually changed, the energy level obtained by the quantum effect can be gradually changed as shown by the dotted line in FIG. That is, the effective energy level of the valence band of the overflow prevention layer 12 gradually changes from the p-type guide layer 107 toward the active layer 106 in a stepwise manner. As a result, the effective barrier to holes is reduced, and holes can flow into the active layer 106 along this step.

On the other hand, in the overflow prevention layer 12, the barrier layer 12BR adjacent to the active layer 106 functions as a barrier for preventing the overflow of electrons from the active layer. That is, the end face of the overflow prevention layer 12 on the active layer side has a large band gap that rises sharply. Therefore, by appropriately setting the composition and the layer thickness, the overflow of electrons can be effectively suppressed. Specifically, in the case of a nitride-based semiconductor laser, the barrier layer 12BR is preferably made of AlGaN (about 25% of aluminum composition) and has a thickness of about 20 nm.

FIG. 3 is a conceptual diagram showing the band structure of the semiconductor light emitting device of the present invention and illustrating the flow of carriers under the condition of a low injection current. As is clear from the comparison with FIG. 11, according to the present invention, the flow of carriers is significantly improved. That is, the overflow prevention layer 12 of the present invention
Facilitates hole flow without high doping. As a result, holes can be caused to flow into the active layer at a lower operating voltage than before, and the operating voltage of the device can be reduced. At the same time, since the concentration of holes in the active layer is greatly increased, recombination of electrons in the active layer is promoted, and the mean free path of electrons is shortened. As a result, it is possible to suppress the overflow of electrons particularly under the condition of low current density. That is, according to the present invention, carrier loss can be suppressed, and luminescence recombination can be caused in the active layer with an extremely high probability.

At the same time, according to the present invention, since the overflow prevention layer 12 functions very effectively, it is not necessary to make the aluminum composition of the cladding layer too high. In general, in a light-emitting element using a nitride-based semiconductor, when a layer having a high aluminum composition is provided, deterioration of characteristics is likely to occur due to crystal distortion, but according to the present invention, the aluminum composition of the cladding layer is reduced. Can be lowered,
It is possible to grow a sufficiently thick cladding layer necessary for confining light without deteriorating characteristics.

FIG. 4 is a graph showing the light output characteristics of the semiconductor light emitting device of the present invention. FIG. 2 shows the relationship between the operating current and the optical output of the semiconductor laser, and also shows the characteristics of the conventional semiconductor laser illustrated in FIG. ADVANTAGE OF THE INVENTION According to this invention, since the loss of a carrier is suppressed very effectively, laser oscillation is promoted and an oscillation threshold current can be made lower than before. In addition, the slope of the optical output with respect to the current in the laser oscillation state, that is, the slope efficiency is greatly improved.

Further, as a result of the lowering of the threshold value and the improvement of the efficiency, the heat generation of the device is reduced and the life of the light emitting device is prolonged.

The overflow prevention layer 12 in the present invention
Is not limited to the specific example shown in FIG. The number of periods of the superlattice constituting the overflow prevention layer and how to change the thickness of each layer can be determined as appropriate. For example, the thickness of each barrier layer may be constant, and only the thickness of the well layer may be gradually changed. Conversely, the thickness of each well layer may be constant, and only the thickness of the barrier layer may be gradually changed. On the other hand, the compositions of the barrier layer and the well layer may be changed simultaneously.

However, it is desirable that the layer thickness of each layer constituting the superlattice is set to a layer thickness that effectively generates a quantum effect. That is, it is desirable that the thickness of each layer be approximately 10 nm (nanometer) or less. Further, the barrier layer 12BR adjacent to the active layer may be formed thicker to effectively suppress the overflow of electrons.

FIG. 5 is a conceptual diagram of a band structure showing a second specific example of the overflow prevention layer of the semiconductor light emitting device of the present invention. That is, FIG.
2 represents the energy level of the valence band. In the example shown in the figure, the overflow prevention layer 12 is made of AlGaN, and the graded portion 12GR whose composition changes continuously and the barrier portion 12B whose value is almost constant.
R. The aluminum composition of the graded portion 12GR continuously increases from the guide layer 107 toward the active layer 106, and is formed so as to maintain a substantially constant value in the barrier portion BR.

By forming such a continuously changing energy level in the graded portion 12GR, the barrier against holes is greatly reduced, and holes are easily transferred from the guide layer 107 to the active layer 106. Will be able to flow in. This example is superior to the example shown in FIG. 2 in that the change in the energy level is extremely smooth.

Such an overflow prevention layer whose composition changes gradually can be formed, for example, by metal organic chemical vapor deposition (MOCV).
It can be formed by gradually changing the flow rate of each source gas when growing by D: metel-organic chemical vapor deposition) method.

In FIG. 5, the graded portion 1
The composition changes continuously in the 2GR, and the barrier portion 12B
Although the case where the composition of R is constant is illustrated, other than this, for example, the barrier portion 12BR may be formed so that the aluminum composition changes.

FIG. 6 is a conceptual diagram of a band structure showing a third specific example of the overflow prevention layer of the semiconductor light emitting device of the present invention. That is, FIG.
2 represents the energy level of the valence band. Also in the example shown in the figure, the overflow prevention layer is made of AlGaN. The aluminum composition is formed so as to increase stepwise from the guide layer 107 toward the active layer 106.

Even in this case, the barrier against holes is greatly reduced, and holes can easily flow into the active layer from the guide layer. On the other hand, as in the specific example described above, by appropriately setting the composition and the layer thickness of the barrier portion 12BR adjacent to the active layer, the overflow of electrons can be effectively suppressed.

According to the study by the present inventors, it has been found that good characteristics can be obtained when the layer thickness of each step of the step is in the range of 5 nm to 20 nm. The number of layers of the stairs is not limited to the illustrated example. However, when the number of layers increases, the resistance of the element tends to increase due to the influence of the interface state or the like. Therefore, it is desirable that the number of layers be about 10 or less.

In this embodiment, the crystal growth is easier than in the above-described second embodiment in that the composition of aluminum is changed stepwise.

On the other hand, the position where the overflow prevention layer 12 is provided is not limited between the active layer and the p-type guide layer.

FIG. 7 is a schematic band structure diagram showing a modification of the semiconductor light emitting device of the present invention. That is, in the device illustrated in FIG.
It is provided between the mold guide layer 107 and the p-type cladding layer 108. Overflow prevention 12 in such a position
Is provided, it is possible to obtain a light emitting element with high luminous efficiency by promoting the flow of holes while preventing the overflow of electrons from the active layer 106.

Also in this modification, the same effect can be obtained by using the various structures described above with reference to FIGS. 2 to 6 as the overflow prevention layer 12.

Further, the overflow prevention layer may be provided on the n side of the light emitting device.

FIG. 8 is a schematic sectional view showing a second modification of the semiconductor light emitting device of the present invention. In the device illustrated in the figure, overflow preventing layers 12A and 12B are provided on both sides of the active layer 106, respectively. As a specific configuration of these overflow prevention layers, any of those described above with reference to FIGS. 2, 5, and 6 can be employed.

In general, in a semiconductor laser using a nitride-based semiconductor, when the oscillation wavelength is longer than 410 nm, the overflow of holes from the active layer does not often cause a problem. However, if the oscillation wavelength is shorter than this, the overflow of holes causes a bad effect, and if the oscillation wavelength is 390 nm or less, a measure for preventing the overflow of holes is required.

In the device illustrated in FIG. 8, the active layer 1
By providing the overflow prevention layer 12B also on the n side of 06, the overflow of holes from the active layer can be effectively suppressed without preventing the inflow of electrons from the n-type guide layer 105. As a result, especially in a short wavelength region, a decrease in luminous efficiency due to loss of carriers is eliminated, and a semiconductor light emitting device with higher efficiency and longer life can be realized.

FIG. 9 is a schematic sectional view showing a third modification of the semiconductor light emitting device of the present invention. In the device illustrated in the figure, the overflow prevention layer 12 is provided between the active layer 106 and the p-type guide layer 107. Here, as the overflow prevention layer, any of those described above with reference to FIGS. 2 to 6 can be employed.

On the other hand, in the present modification, the n-type cladding layer 116 and the p-type cladding layer 117 are each formed of a superlattice. Specifically, these cladding layers are respectively composed of a barrier layer of AlGaN (aluminum composition 14%, layer thickness 2.5 nm) and a GaN (layer thickness 2.5 nm).
The superlattice structure can be obtained by alternately laminating about 120 periods with the well layers described above.

When the cladding layers 116 and 117 have such a superlattice structure, a so-called multiple quantum barrier (MQB) effect can be obtained.
The effect of confining carriers by the cladding layer can be further improved.

In the illustrated example, the overflow prevention layer 12 is provided between the active layer 106 and the p-type guide layer 107. In addition, for example, the overflow prevention layer 12 may be a p-type guide layer. 107 and cladding layer 11
7 may be provided. Further, it may be provided between the active layer 106 and the n-type guide layer 105 or between the n-type clad layer 116 and the n-type guide layer 105.

The embodiments of the invention have been described with reference to examples. However, the present invention is not limited to these specific examples.

That is, each of the specific examples described above can be applied to a semiconductor laser and a light emitting diode in the same manner to obtain the respective effects.

Further, the conductivity type of each semiconductor layer shown in each specific example can be similarly inverted.

The substrate that can be used as the substrate is not limited to the above-mentioned sapphire, but may be, for example, spinel, ScAlMgO ₄ , LaSrGaO ₄ ,
An insulating substrate such as (LaSr) (AlTa) O ₃ ,
Conductive substrates such as iC, MgO, Si, and GaAs can be similarly used to obtain the respective effects.

Further, in the above specific example, the semiconductor laser using the nitride semiconductor has been described.
The present invention also provides an AlGaAs-based, GaP-based,
A similar effect can be obtained by applying the present invention to a semiconductor light emitting device using various material systems such as an InGaAlP system, an InP system, a SiC system, and a ZnSSe system.

[0071]

The present invention is embodied in the form described above, and has the following effects.

That is, according to the present invention, by introducing an overflow prevention layer having a unique structure, it is possible to suppress the overflow of electrons and facilitate the flow of holes without performing high doping. As a result, holes can be caused to flow into the active layer at a lower operating voltage than before, and the operating voltage of the device can be reduced.

At the same time, according to the present invention, since the concentration of holes in the active layer is greatly increased, recombination of electrons in the active layer is promoted, and the mean free path of electrons is shortened. As a result, it is possible to suppress the overflow of electrons particularly under the condition of low current density. That is, according to the present invention, carrier loss can be suppressed, and luminescence recombination can be caused in the active layer with an extremely high probability.

Further, according to the present invention, since the overflow prevention layer works extremely effectively, it is not necessary to make the aluminum composition of the cladding layer too high. As a result, without deteriorating characteristics due to crystal distortion,
It is possible to grow a sufficiently thick cladding layer necessary for confining light.

That is, according to the present invention, since the loss of carriers is extremely effectively suppressed, laser oscillation is promoted and the oscillation threshold current can be reduced as compared with the prior art. In addition, the slope of the optical output with respect to the current in the laser oscillation state, that is, the slope efficiency is greatly improved.

Further, as a result of the lowering of the threshold value and the improvement of the efficiency, the heat generation of the element is reduced and the life of the light emitting element is prolonged.

As described above, according to the present invention, various types of semiconductor light emitting devices having high performance and high reliability can be provided, and industrial advantages are great.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a semiconductor light emitting device of the present invention.

FIG. 2 is a conceptual diagram of a valence band structure showing a specific example of an overflow prevention layer of the semiconductor light emitting device of the present invention.

FIG. 3 shows a band structure of the semiconductor light emitting device of the present invention,
FIG. 4 is a conceptual diagram illustrating a flow of carriers under a condition of a low injection current.

FIG. 4 is a graph showing light output characteristics of the semiconductor light emitting device of the present invention.

FIG. 5 is a conceptual diagram of a band structure showing a second specific example of the overflow prevention layer of the semiconductor light emitting device of the present invention.

FIG. 6 is a conceptual diagram of a band structure showing a third specific example of the overflow prevention layer of the semiconductor light emitting device of the present invention.

FIG. 7 is a schematic band structure diagram showing a modification of the semiconductor light emitting device of the present invention.

FIG. 8 is a schematic sectional view showing a second modification of the semiconductor light emitting device of the present invention.

FIG. 9 is a schematic sectional view illustrating a third modification of the semiconductor light emitting device of the present invention.

FIG. 10 is a schematic sectional view showing a conventional semiconductor laser provided with a cap layer.

11 is a conceptual diagram illustrating a band structure of the device of FIG. 10 and illustrating a flow of carriers under a condition of a low injection current.

[Explanation of symbols]

 Reference Signs List 12 overflow prevention layer 101 substrate 102 n-type contact layer 103 n-side electrode 104 n-type clad layer 105 n-type guide layer 106 active layer 107 p-type guide layer 108 p-type clad layer 109 p-type contact layer 110 protective film 111 p-side electrode 112 cap layer

Claims (6)

[Claims] 1. A semiconductor light emitting device comprising an active layer, wherein electrons and holes are injected into the active layer to generate light, and wherein any one of the electrons and the holes injected into the active layer is provided. The semiconductor device further includes an overflow prevention layer acting as a barrier that suppresses one overflow, wherein the overflow prevention layer further reduces a barrier effect on one of the electron and the hole before being injected into the active layer. A semiconductor light emitting device, comprising: 2. A semiconductor light emitting device comprising: an active layer; and an overflow prevention layer, wherein the semiconductor layer emits light by injecting electrons and holes into the active layer, wherein the overflow prevention layer comprises: an active layer. The end face on the side has a first band gap that is larger than the active layer and changes steeply. On the opposite side as viewed from the active layer, the effective band gap becomes closer to the end face in the layer thickness direction. A semiconductor light emitting device, wherein the semiconductor light emitting device is configured to be smaller than the first band gap. 3. The overflow prevention layer has a superlattice including a plurality of barrier layers and a plurality of well layers, and at least one of the plurality of barrier layers and the plurality of well layers has a layer thickness or a composition. 3. The semiconductor light-emitting device according to claim 1, wherein is not constant. 4. The semiconductor light emitting device according to claim 1, wherein the overflow prevention layer has a portion whose composition continuously changes along a thickness direction of the layer. 5. The semiconductor light emitting device according to claim 1, wherein the overflow prevention layer has a portion where the composition changes stepwise along the layer thickness direction. 6. The semiconductor according to claim 1, wherein said active layer is made of a nitride semiconductor, and said overflow prevention layer is made of a nitride semiconductor containing aluminum. Light emitting element.